Let's talk about brake fluid

[secondchance]

ZR-1 guys are pretty meticulous about all fluids going into our cars. Right?
We are periodically having serious discussion on engine oil (brand, ZDDP content, etc.), tranny fluid, differential fluid, engine coolant (green stuff, Dexcool, even Evans).
What about brake fluid?
Our cars came with DOT 3 fluid and that was about 24 to 29 years ago. Been awhile, huh!
I use to use Advance Auto Part off the shelf DOT3 such as Valvoline, Wagner, etc. Then about 3-4 years ago when I modified my brakes with Wilwood calipers/rotors, I asked Jim Jandick and he recommended Wilwood EXP 600 plus - DOT 4 fluid with high boiling point.
As I looked into the subject, I find DOT 4 stuff is good from boiling point but not so good when it comes to longevity due to faster water absorption.
Now we have DOT 5, silicone based fluid not to be used with ABS, and DOT 5.1, glycol based similar to DOT 3 and DOT 4, which can be used with ABS.
As I was getting lost, I called Wilwood and talked to their rep. Took awhile but he confirmed Wilwood High Temp 570 is DOT 3 but would not answer service interval - understandable.
So, the question is what do you guys use? I know most ZR-1s are occasional use cars and often put away for the winter. Also, we might have a chemical engineer or automotive engineer among us.
Any thoughts?

[BYEBYE2U]

You just gave the answer to 99% of ZR1s..
Most of the time they sit in the garage so DOT 3 or 4 are more than enough.
The Zs that do high speed braking n have high braking surface areas can use a higher boiling point fluid.
I use Castrol GT LMA (Low Moisture Activity) synthetic brake fluid in my drag car.
No issues at 145+mph stops last 5-7 years
If one day you take your car out n the brake pedal feels "STIFF" n or cars does not stop like you're used to: It's time to change fluid
Same goes for slave cylinder n clutch disengagement.

[Dynomite]

Concur.....I use Dot 3 and Dot 4 in all Zs with a couple having Wilwood C5 Z06 Conversions.

Post 3 - LT5/ZR-1 Fluids (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070550)

[Hib Halverson]

I get my brake fluid from either of two sources, either Willwood, which brands it high-perf. fluid "EXP 600" or Red Line which brands its fluid as "RL600".

Both of these are DOT4 rated but they exceed the DOT specs as far as dry and wet boiling points.

[Young1]

At Christmas just flushed and filled with MOTUL 600 DOT 4. It has a slightly higher wet boiling point than others and is priced right on Amazon. Remember dry boiling point only applies the moment you fill it.

[Vette Guy]

I race with Pentosin Super Dot 4, (just over 500 dry boiling point) in the ‘88 with J55 calipers and have never cooked the brakes even with slicks. I’m also running DRM stainless caliper pistons and have brake cooling duct hoses. I threshold brake and run 30 min sessions. It’s very reasonably priced and what I use in my Z. On the ‘96 race car (WC GT), I run Amsoil Dominator brake fluid (410 wet/ 580 dry) with Coleman calipers up front with cooling ducts and J55s on the rear (threshold brake at much higher speeds). With street tires, I’d think Super Dot 4 would be more than adequate for a track day. That said, I always flush fluid before every event. If you run HPDEs and want to sleep well, I’m sure Motul, Redline or Wilwood 600 won’t let you down. Still, Amsoil Dominator has one of the best wet boiling points of 410 if you want to fill and forget for a year.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Paul Workman]

I race with Pestolin Super Dot 4, (just over 500 dry boiling point) in the ‘88 with J55 calipers and have never cooked the brakes even with slicks. I’m also running DRM stainless caliper pistons and have brake cooling duct hoses. I threshold brake and run 30 min sessions. It’s very reasonably priced and what I use in my Z. On the ‘96 race car (WC GT), I run Amsoil Dominator brake fluid (410 wet/ 580 dry) with Coleman calipers up front with cooling ducts and J55s on the rear (threshold brake at much higher speeds). With street tires, I’d think Super Dot 4 would be more than adequate for a track day. That said, I always flush fluid before every event. If you run HPDEs and want to sleep well, I’m sure Motul, Redline or Wilwood 600 won’t let you down. Still, Amsoil Dominator has one of the best wet boiling points of 410 if you want to fill and forget for a year.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

Thanks 4 the insight - coming from a "track guy", that is the kind of recommendation we occasional WARRIORS can appreciate!:thumbsup:

3(?) years ago during a sprint on "Tail of the Dragon", several who were there on that run got a first-hand lesson about brake fluid maintenance.

Fortunately, the (new GS) driver was able to down-shift and with the e-brake get stopped at a pull-over spot w/o incident except a good scaring! He was able to tip-toe in low gears to the bottom where there was a large turn-out where Mr. FIX-IT (aka Jim Voter) pulled a bottle of fresh brake fluid from his emergency kit and a lesson on bleeding brakes ensued.

Point well taken: Part of one's annual spring routine should be bleeding the brakes - replacing the fluid. And, don't forget the clutch and power steering too, especially if you do or plan to do any aggressive driving (speaking from the "School of Hard Knocks" here!).

Gonna be 50º and sunny in Chicagoland today. Maybe I should heat up MY brakes a bit today?

[tnova]

I've run both ATE and Wilwood DOT 4 brake fluid on the racetrack for eight years, only recently switching to Wilwood after losing my source of reasonably priced ATE. No problems with either one on the track including extremely hard braking at Auto Club Speedway coming off the oval into the infield section of the course (135+ mph to 40-50 mph). I buy brake fluid by the case - $ ouch.


I absolutely bleed brakes and clutch prior to each event and flush twice a year. If, when bleeding brakes, I see dirty or milky fluid I totally flush but also find the source and repair. However that scenario has always been proceeded by the pedal getting soft or even a double pump required when braking, so I was hunting for the problem. Usually it's been failing seals around the caliper pistons or in the master cylinders. Some performance brake pad materials are extremely corrosive (Hawk Blue) and it needs to be cleaned off the calipers and wheel bearing seals after each event or it deteriorates the seals and permits intrusion into the closed braking system.


For cars that I run on the track, autocross, or even on aggressive runs, I perform a total lubricant replacements (clutch, trans or transaxle, differential, wheel bearings, power steering) once a year. If I had an "off" causing billowing dirt (Willow Springs, Streets of Willow, Chuckwalla) or into sand (Spring Mountain) I replace fluids. Fortunately that was the has not been necessary the last many years but I have dropped a wheel now and then.


No issues running either one on the street.


Tony - Tnova

[secondchance]

I see quite a few who track their cars. Any thoughts on conversion to larger bore brake master? Am I right that later C4s have 7/8” bore? I heard tracked C4s using Suburban master. I am running 6 piston front and 4 piston Wilwood calipers and thinking larger bore master would shorten pedal travel and firm up the pedal feel. Thoughts?

[tnova]

As for master cylinders, you'll get many different opinions and a discussion on volume vs. pressure as well as stock master cylinders with and without a modified bias spring. The real answer is that it depends on your individual system. Questions to ask:
- Is your pedal firm?
- Is your pedal travel too much or too little?
- Are your brakes balanced front to rear, i.e. will the fronts lock up just a little, a very little before the rears? You need to pull the ABS fuse to test.


The '90 and '91 ZR-1s have the smallest bore master cylinders, 7/8".


On my ZR-1 with Wilwood 6-piston on the front and stock calipers on rear, I could not get the front to rear balance adjusted so the fronts locked up just prior to the rears. I installed a bias valve and it improved but still not enough front brake before the rears locked up. I contacted Wilwood and they advised going to a bigger bore master cylinder from a later model ZR-1, other GM adaptation, or an aftermarket system in order to get enough volume to the front pistons as mine was a volume issue over a pressure issue.


Using an old C4 racers solution, I installed a 4th generation Camaro master cylinder which has a 1" bore. A spacer is required between the booster and master cylinder to keep the distance on the piston shaft to pedal shaft length correct. Others have used Suburban master cylinders. Others have gotten satisfactory results with a later model ZR-1 master cylinder with modified bias spring and/or a bias valve.


So, find an abandoned street or large parking lot, disable your ABS and have someone observe your lockup as you do max braking from about 40-50 mph. Not your pedal feel and travel also. Then call Wilwood since you have their setup. Make sure you tell them what year ZR-1 you have so they know what size bore your master cylinder is.


I'll PM you a document with a summary of posts and solutions on the brake master cylinder.

[secondchance]

I never knew there was master bore size change between early vs. later Z. My ZR-1 is a 94. Would you know master bore size?
Pedal seems a bit softer than it use to be. Could be due to brake fluid being 2 years old Wilwood EXP 600. Pedal travel is reasonable but I favor shorter firm pedal.
I have not tested front vs. rear lock up test. I’ll have to try your suggestion.

[tnova]

Your bore size is 15/16". Here's part of the write-up I PM'd you. Note that you may have to modify the ends of the brake lines for different thread sizes if you switch master cylinders. I don't have the details on the Suburban master cylinder. I also don't know about later model C5/6/7 MCs which I've heard of people adapting:




I first became aware ofthe problem when A friend installed some Wilwoods 6p calipers on his car.Braking was better but nowhere near impressive. The car stopped well but wouldnot get the ABS excited enough to engage. That’s because his 6 pistons requiredLOTS more volume to move against the rotor. No volume = no movement. Untilthere is enough volume transmitted from the MC the caliper can only move asmuch as the fluid allows. When you're trying to move big pistons or lots ofsmall pistons you have to move more fluid to get the same results as before.Basic hydraulics.

The same problem exists on my car with thebigger 2 piston calipers. They need twice the fluid that the MC was deliveringbefore. OR...a longer stroke. That’s what I do not want...is to push the pedalto the floor. Takes too long and the recovery time becomes an issue when thepedal is somewhere in between full ready and bottomed out.

I've seen a C4 system that was set up with abigger MC and the difference will throw your eyeballs out of their sockets whenyou hit the brakes hard...

That car was set up with a kit the guy boughtbut has no idea of what kind of MC it is or where it came from. Someone foundit somewhere that he can no longer locate.....


The bias spring will notfix the problem. The problem has been solved by few people. They installed aCamaro MC and claim great results. This is something I got to do.


87 master Brake MasterCylinder
Bore Size : 7/8"
Line thread Size : M12-1, M10-1


The '88-'91 master cylinder
Bore size: 7/8"
Line thread size 12M x 1 and 10M x 1


The '92-'94 master cylinder
Bore size 15/16"
Line thread size 12M x 1 and 10M x 1


The '95-'96 master cylinder
Bore size 15/16"
Line thread size 12M x 1 and 10M x 1


98-2002 Camaro = 1" bore
Bore Size 1"
Line thread size 11mx1.5 and 12mx1

[secondchance]

I appreciate the info.:cheers: